Substituted N-oxide pyrazine derivatives

ABSTRACT

N-oxide pyrazine derivatives represented by formula (I) or a salt thereof, or a solvate thereof or a hydrate thereof: 
     
       
         
         
             
             
         
       
         
         
           
             wherein: 
             R1, R2, R3, R4, and R5 are as defined in the disclosure. Also disclosed are methods of preparing the compounds of formula (I) and their use in therapeutics.

This application is a continuation of International Application No. PCT/IB2009/006445, filed Jun. 25, 2009, which is incorporated herein by reference in its entirety; which claims the benefit of priority of European Patent Application No. 08290619.9 filed Jun. 26, 2008.

TECHNICAL FIELD

The present invention relates to compounds that are useful as an active ingredient of a medicament for preventive and/or therapeutic treatment of neurodegenerative diseases caused by abnormal activity of GSK3β.

BACKGROUND ART

GSK3β (glycogen synthase kinase 3β) is a proline directed serine, threonine kinase that plays an important role in the control of metabolism, differentiation and survival. It was initially identified as an enzyme able to phosphorylate and hence inhibit glycogen synthase. It was later recognized that GSK3β was identical to tau protein kinase 1 (TPK1), an enzyme that phosphorylates tau protein in epitopes that are also found to be hyperphosphorylated in Alzheimer's disease and in several tauopathies.

Interestingly, protein kinase B (AKT) phosphorylation of GSK3β results in a loss of its kinase activity, and it has been hypothesized that this inhibition may mediate some of the effects of neurotrophic factors. Moreover, phosphorylation by GSK3β of β-catenin, a protein involved in cell survival, results in its degradation by an ubiquitinilation dependent proteasome pathway.

Thus, it appears that inhibition of GSK3β activity may result in neurotrophic activity. Indeed there is evidence that lithium, an uncompetitive inhibitor of GSK3β, enhances neuritogenesis in some models and also increases neuronal survival, through the induction of survival factors such as Bcl-2 and the inhibition of the expression of proapoptotic factors such as p53 and Bax.

Recent studies have demonstrated that β-amyloid increases the GSK3β activity and tau protein phosphorylation. Moreover, this hyperphosphorylation as well as the neurotoxic effects of β-amyloid are blocked by lithium chloride and by a GSK3β antisense mRNA. These observations strongly suggest that GSK3β may be the link between the two major pathological processes in Alzheimer's disease: abnormal APP (Amyloid Precursor Protein) processing and tau protein hyperphosphorylation.

Although tau hyperphosphorylation results in a destabilization of the neuronal cytoskeleton, the pathological consequences of abnormal GSK3β activity are, most likely, not only due to a pathological phosphorylation of tau protein because, as mentioned above, an excessive activity of this kinase may affect survival through the modulation of the expression of apoptotic and antiapoptotic factors. Moreover, it has been shown that β-amyloid-induced increase in GSK3β activity results in the phosphorylation and, hence the inhibition of pyruvate dehydrogenase, a pivotal enzyme in energy production and acetylcholine synthesis.

Altogether these experimental observations indicate that GSK3β may find application in the treatment of the neuropathological consequences and the cognitive and attention deficits associated with Alzheimer's disease, as well as other acute and chronic neurodegenerative diseases and other pathologies where GSK3β is deregulated (Nature reviews Vol. 3, June 2004, p. 479-487; Trends in Pharmacological Sciences Vol. 25 No. 9, September 2004, p. 471-480; Journal of neurochemistry 2004, 89, 1313-1317; Medicinal Research Reviews, Vol. 22, No. 4, 373-384, 2002).

The neurodegenerative diseases include, in a non-limiting manner, Parkinson's disease, tauopathies (e.g. Fronto temporal dementia, corticobasal degeneration, Pick's disease, progressive supranuclear palsy), Wilson's disease, Huntington's disease (The Journal of biological chemistry Vol. 277, No. 37, Issue of September 13, pp. 33791-33798, 2002), Prion disease (Biochem. J. 372, p. 129-136, 2003) and other dementia including vascular dementia; acute stroke and other traumatic injuries; cerebrovascular accidents (e.g. age related macular degeneration); brain and spinal cord trauma; amyotrophic lateral sclerosis (European Journal of Neuroscience, Vol. 22, pp. 301-309, 2005) peripheral neuropathies; retinopathies and glaucoma. Recent studies have also shown that inhibition of GSK3β results in neuronal differentiation of embryonic stem cells (ESC) and support the renewal of human and mouse ESCs and the maintenance of their pluripotency. This suggests that inhibitors of GSK3β could have applications in regenerative medicine (Nature Medicine 10, p. 55-63, 2004).

Inhibitors of GSK3β may also find application in the treatment of other nervous system disorders, such as bipolar disorders (manic-depressive illness). For example lithium has been used for more than 50 years as a mood stabilizer and the primary treatment for bipolar disorder. The therapeutic actions of lithium are observed at doses (1-2 mM) where it is a direct inhibitor of GSK3β. Although the mechanism of action of lithium is unclear, inhibitors of GSK3β could be used to mimic the mood stabilizing effects of lithium. Alterations in Akt-GSK3β signaling have also been implicated in the pathogenesis of schizophrenia.

In addition, inhibition of GSK3β could be useful in treating cancers, such as colorectal, prostate, breast, non-small cell lung carcinoma, thyroid cancer, T or B-cell leukaemia and several virus-induced tumours. For example, the active form of GSK3β has been shown to be elevated in the tumors of colorectal cancer patients and inhibition of GSK3β in colorectal cancer cells activates p53-dependent apoptosis and antagonizes tumor growth. Inhibition of GSK3β also enhances TRAIL-induced apoptosis in prostate cancer cell lines. GSK3β also plays a role in the dynamics of the mitotic spindle and inhibitors of GSK3β prevent chromosome movement and lead to a stabilization of microtubules and a prometaphase-like arrest that is similar to that observed with low doses of Taxol. Other possible applications for GSK3β inhibitors include therapy for non-insulin dependent diabetes (such as diabetes type II), obesity and alopecia.

Inhibitors of human GSK3β may also inhibit pfGSK3, an ortholog of this enzyme found in Plasmodium falciparum, as a consequence they could be used for the treatment of malaria (Biochimica et Biophysica Acta 1697, 181-196, 2004). Recently, both human genetics and animal studies have pointed out the role of Wnt/LPR5 pathway as a major regulator of bone mass accrual. Inhibition of GSK3β leads to the consequent activation of canonical Wnt signaling. Because deficient Wnt signaling has been implicated in disorders of reduced bone mass, GSK3β inhibitors may also be used for treating disorders of reduced bone mass, bone-related pathologies, osteoporosis. According to recent data, GSK3β inhibitors might be used in the treatment or prevention of Pemphigus vulgaris.

Recent studies show that GSK3beta inhibitor treatment improves neutrophil and megakaryocyte recovery. Therefore, GSK3beta inhibitors will be useful for the treatment of neutropenia induced by cancer chemotherapy. Previous studies have shown that GSK3 activity decreases LTP, a electrophysiological correlate of memory consolidation, suggesting that inhibitor of this enzyme may have procognitive activity. Procognitive effects of the compound could find application for the treatment of memory deficits characteristic of Alzheimer's disease, Parkinson disease, age-associated memory impairment, mild cognitive impairment, brain trauma, schizophrenia and other conditions in which such deficits are observed. Inhibitors of GSK3β may also find application in the treatment of parenchymal renal diseases (Nelson P J, Kidney International Advance online publication 19 Dec. 2007) and in the prevention or treatment of muscle atrophy (J. Biol. Chem (283) 2008, 358-366)

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide compounds useful as an active ingredient of a medicament for preventive and/or therapeutic treatment of a disease caused by abnormal GSK3β activity, more particularly of neurodegenerative diseases. More specifically, the object is to provide novel compounds useful as an active ingredient of a medicament that enables prevention and/or treatment of neurodegenerative diseases such as Alzheimer's disease.

Thus, the inventors of the present invention have identified compounds possessing inhibitory activity against GSK3β. As a result, they found that compounds represented by the following formula (I) had the desired activity and were useful as an active ingredient of a medicament for preventive and/or therapeutic treatment of the aforementioned diseases.

The present invention thus provides as an object of the invention the N-oxide pyrazine derivatives represented by formula (I) or salts thereof, solvates thereof or hydrates thereof:

wherein:

-   R1 represents a 4-pyridine ring, a halogen atom; -   R2 represents a hydrogen atom; -   R3 represents a hydrogen atom; -   R4 represents:     -   a phenylC₁₋₃alkyl group, this group being optionally substituted         by 1 to 4 substituents selected from a C₁₋₆ alkyl group, a         halogen atom, a C₁₋₂ perhalogenated alkyl group, a C₁₋₃         halogenated alkyl group, a hydroxyl group, a C₁₋₆ alkoxy group,         a C₁₋₂ perhalogenated alkoxy group, a C₁₋₆ alkylsulfonyl group,         a nitro, a cyano, an amino, a C₁₋₆ monoalkylamino group or a         C₂₋₁₂ dialkylamino group, an acetoxy group, an aminosulfonyl         group; -   R5 represents a hydrogen atom;     -   in the form of a free base or of an addition salt with an acid.

According to another aspect of the present invention, there is provided a medicament comprising as an active ingredient a substance selected from the group consisting of the N-oxide pyrazine derivatives represented by formula (I) and the physiologically acceptable salts thereof, and the solvates thereof and the hydrates thereof. As preferred embodiments of the medicament, there are provided the aforementioned medicament which is used for preventive and/or therapeutic treatment of diseases caused by abnormal GSK3β activity, and the aforementioned medicament which is used for preventive and/or therapeutic treatment of neurodegenerative diseases and in addition other diseases such as:

Non-insulin dependent diabetes (such as diabetes type II) and obesity; malaria, bipolar disorders (manic depressive illness); schizophrenia; alopecia or cancers such as colorectal, prostate, breast cancer, non-small cell lung carcinoma, thyroid cancer, T or B-cell leukaemia, several virus-induced tumours and bone related pathologies; the treatment of parenchymal renal diseases and in the prevention or treatment of muscle atrophy; the treatment of cognitive and memory deficit. The medicament could also find an application in regenerative medicine.

As further embodiments of the present invention, there are provided the aforementioned medicament wherein the diseases are neurodegenerative diseases and are selected from the group consisting of Alzheimer's disease, Parkinson's disease, tauopathies (e.g. Fronto temporal dementia, corticobasal degeneration, Pick's disease, progressive supranuclear palsy), Wilson's disease, Huntington's disease, Prion disease and other dementia including vascular dementia; acute stroke and others traumatic injuries; cerebrovascular accidents (e.g. age related macular degeneration); brain and spinal cord trauma; amyotrophic lateral sclerosis; peripheral neuropathies; retinopathies and glaucoma, and the aforementioned medicament in the form of pharmaceutical composition containing the above substance as an active ingredient together with one or more pharmaceutical additives. As further embodiments of the present invention, there are provided the aforementioned medicament wherein the bones related pathologies are osteoporosis. The present invention further provides an inhibitor of GSK3β activity comprising as an active ingredient a substance selected from the group consisting of the N-oxide pyrazine derivatives of formula (I) and the salts thereof, and the solvates thereof and the hydrates thereof.

According to further aspects of the present invention, there is provided a method for preventive and/or therapeutic treatment of neurodegenerative diseases caused by abnormal GSK3β activity, which comprises the step of administering to a patient a preventively and/or therapeutically effective amount of a substance selected from the group consisting of N-oxide pyrazine derivatives of formula (I) and the physiologically acceptable salts thereof, and the solvates thereof and the hydrates thereof; and a use of a substance selected from the group consisting of the N-oxide pyrazine derivatives of formula (I) and the physiologically acceptable salts thereof, and the solvates thereof and the hydrates thereof for the manufacture of the aforementioned medicament.

As used herein, the C₁₋₆ alkyl group represents a straight or branched or cyclo alkyl group having 1 to 6 carbon atoms, optionally substituted by a straight, branched or cyclic C₁₋₆ alkyl group, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, 1,1-dimethylpropyl group, n-hexyl group, isohexyl group, cyclopropylmethyl group and the like.

The C₂₋₁₂ dialkylamino group represents an amino group substituted by two C₁₋₆ alkyl groups, for example, dimethylamino group, ethylmethylamino group, diethylamino group, methylpropylamino group and diisopropylamino group and the like;

The “phenylC₁₋₃alkyl group, this group being optionally substituted” represent an optional substitution on the alkyl part or the phenyl part of the phenylC₁₋₃alkyl group

A leaving group L represents a group which could be easily cleaved and substituted; such a group may be for example a tosyl, a mesyl, a bromide and the like.

The compounds represented by the aforementioned formula (I) may form a salt. Examples of the salt include, when an acidic group exists, salts of alkali metals and alkaline earth metals such as lithium, sodium, potassium, magnesium, and calcium; salts of ammonia and amines such as methylamine, dimethylamine, trimethylamine, dicyclohexylamine, tris(hydroxymethyl)aminomethane, N,N-bis(hydroxyethyl)piperazine, 2-amino-2-methyl-1-propanol, ethanolamine, N-methylglucamine, and L-glucamine; or salts with basic amino acids such as lysine, δ-hydroxylysine and arginine. The base-addition salts of acidic compounds are prepared by standard procedures well known in the art.

When a basic group exists, examples include salts with mineral acids such as hydrochloric acid, hydrobromic acid; salts with organic acids such as acetic acid, propionic acid, tartaric acid, fumaric acid, maleic acid, malic acid, oxalic acid, succinic acid, citric acid, benzoic acid and the like.

The acid-addition salts of the basic compounds are prepared by standard procedures well known in the art which include, but are not limited thereto, dissolving the free base in an aqueous alcohol solution containing the appropriate acid and isolating the salt by evaporating the solution, or by reacting the free base and an acid in an organic solvent, in which case the salt separates directly, or is precipitated with a second organic solvent, or can be obtained by concentration of the solution. The acids which can be used to prepare the acid-addition salts include preferably those which produce, when combined with the free base, pharmaceutically-acceptable salts, that is, salts whose anions are relatively innocuous to the animal organism in pharmaceutical doses of the salts, so that the beneficial properties inherent in the free base are not compromised by side effects ascribable to the anions. Although medicinally acceptable salts of the basic compounds are preferred, all acid-addition salts are within the scope of the present invention.

In addition to the N-oxide pyrazine derivatives represented by the aforementioned formula (I) and salts thereof, their solvates and hydrates also fall within the scope of the present invention.

The N-oxide pyrazine derivatives represented by the aforementioned formula (I) may have one or more asymmetric carbon atoms. As for the stereochemistry of such asymmetric carbon atoms, they may independently be either in (R) or (S) configuration, and the derivative may exist as stereoisomers such as optical isomers, or diastereoisomers. Any stereoisomers in pure form, any mixtures of stereoisomers, racemates and the like fall within the scope of the present invention.

In a first embodiment of the invention, there is provided compounds

wherein:

-   R1 represents a 4-pyridine ring, a halogen atom; -   R2 represents a hydrogen atom; -   R3 represents a hydrogen atom; -   R4 represents: a phenylC₁₋₃alkyl group, this group being optionally     substituted by 1 to 4 substituents selected from a halogen atom, a     hydroxyl group; -   R5 represents a hydrogen atom;     -   in the form of a free base or of an addition salt with an acid.         Examples of compounds of the present invention are shown in         table 1 hereinafter. However, the scope of the present invention         is not limited by these compounds. The nomenclature is given         according to IUPAC rules.

A further object of the present invention includes the group of compounds of table 1 of formula as defined hereunder:

-   -   1. N-(2-phenylethyl)-6-pyridin-4-ylpyrazin-2-amine 4-oxide     -   2.         (+/−)2-[(4-oxido-6-pyridin-4-ylpyrazin-2-yl)amino]-1-phenylethanol     -   3.         (+/−)6-2-[(6-chloro-4-oxidopyrazin-2-yl)amino]-1-phenylethanol     -   4. 6-chloro-N-(2-phenylethyl)pyrazin-2-amine 4-oxide

As a further object, the present invention concerns also methods for preparing the N-oxide pyrazine compounds represented by the aforementioned formula (I).

These compounds can be prepared, for example, according to methods explained below.

Preparation Method

N-oxide pyrazine compounds represented by the aforementioned formula (I), may be prepared according to the method described in the scheme 1.

(In the above scheme the definition of R1, R2, R3, R4, R5 are the same as those already described for compound of formula (I)). According to this method, the amine of formula (III), wherein R5 and R4 are defined for compound of formula (I), is allowed to react with a compound of formula (II), at a suitable temperature ranging from 25° to 180° C. under ordinary air to obtain a compound of formula (I). When R1 represents a halogen atom, the compound of formula (I) is allowed to react with a compound of formula (IV), wherein M represents a boronic acid or a stannyl group. The reaction may be carried out in the usual well known coupling reaction such as Suzuki or Stille reactions to afford the compound of formula (I).

Compounds of formula (II), (III) and (IV) are commercially available or may be synthesized according to well-known methods to one skilled in the art.

The compounds of the present invention have inhibitory activity against GSK3β. Accordingly, the compounds of the present invention are useful as an active ingredient for the preparation of a medicament, which enables preventive and/or therapeutic treatment of a disease caused by abnormal GSK3β activity and more particularly of neurodegenerative diseases such as Alzheimer's disease. In addition, the compounds of the present invention are also useful as an active ingredient for the preparation of a medicament for preventive and/or therapeutic treatment of neurodegenerative diseases such as Parkinson's disease, tauopathies (e.g. Fronto temporal dementia, corticobasal degeneration, Pick's disease, progressive supranuclear palsy), Wilson's disease, Huntington's disease, Prion disease and other dementia including vascular dementia; acute stroke and others traumatic injuries; cerebrovascular accidents (e.g. age related macular degeneration); brain and spinal cord trauma; amyotrophic lateral sclerosis, peripheral neuropathies; retinopathies and glaucoma; and other diseases such as non-insulin dependent diabetes (such as diabetes type II) and obesity; malaria, manic depressive illness; schizophrenia; alopecia; cancers such as colorectal, prostate breast cancer, non-small cell lung carcinoma, thyroid cancer, T or B-cell leukemia, several virus-induced tumours and in bone related pathologies; parenchymal renal diseases or muscle atrophy. The medicament could also find an application in regenerative medicine. The medicament could also find an application in the treatment or prevention of Pemphigus vulgaris. The medicament could also find an application in the treatment of neutropenia induced by cancer chemotherapy. The medicament could also find an application for therapeutic treatment of a disease characterized by cognitive and memory deficits such as in Alzheimer's disease, Parkinson disease, age associated memory impairment, mild cognitive impairment, brain trauma, schizophrenia and other conditions in which such deficits are observed.

The present invention further relates to a method for treating neurodegenerative diseases caused by abnormal activity of GSK3β and of the aforementioned diseases which comprises administering to a mammalian organism in need thereof an effective amount of a compound of the formula (I).

As the active ingredient of the medicament of the present invention, a substance may be used which is selected from the group consisting of the compound represented by the aforementioned formula (I) and pharmacologically acceptable salts thereof, and solvates thereof and hydrates thereof. The substance, per se, may be administered as the medicament of the present invention; however, it is desirable to administer the medicament in a form of a pharmaceutical composition which comprises the aforementioned substance as an active ingredient and one or more pharmaceutical additives. As the active ingredient of the medicament of the present invention, two or more of the aforementioned substances may be used in combination. The above pharmaceutical composition may be supplemented with an active ingredient of another medicament for the treatment of the above mentioned diseases. The type of pharmaceutical composition is not particularly limited, and the composition may be provided as any formulation for oral or parenteral administration. For example, the pharmaceutical composition may be formulated, for example, in the form of pharmaceutical compositions for oral administration such as granules, fine granules, powders, hard capsules, soft capsules, syrups, emulsions, suspensions, solutions and the like, or in the form of pharmaceutical compositions for parenteral administrations such as injections for intravenous, intramuscular, or subcutaneous administration, drip infusions, transdermal preparations, transmucosal preparations, nasal drops, inhalants, suppositories and the like. Injections or drip infusions may be prepared as powdery preparations such as in the form of lyophilized preparations, and may be used by dissolving just before use in an appropriate aqueous medium such as physiological saline. Sustained-release preparations such as those coated with a polymer may be directly administered intracerebrally.

Types of pharmaceutical additives used for the manufacture of the pharmaceutical composition, content ratios of the pharmaceutical additives relative to the active ingredient, and methods for preparing the pharmaceutical composition may be appropriately chosen by those skilled in the art. Inorganic or organic substances or solid or liquid substances may be used as pharmaceutical additives. Generally, the pharmaceutical additives may be incorporated in a ratio ranging from 1% by weight to 90% by weight based on the weight of an active ingredient.

Examples of excipients used for the preparation of solid pharmaceutical compositions include, for example, lactose, sucrose, starch, talc, cellulose, dextrin, kaolin, calcium carbonate and the like. For the preparation of liquid compositions for oral administration, a conventional inert diluent such as water or a vegetable oil may be used. The liquid composition may contain, in addition to the inert diluent, auxiliaries such as moistening agents, suspension aids, sweeteners, aromatics, colorants, and preservatives. The liquid composition may be filled in capsules made of an absorbable material such as gelatin. Examples of solvents or suspension mediums used for the preparation of compositions for parenteral administration, e.g. injections, suppositories, include water, propylene glycol, polyethylene glycol, benzyl alcohol, ethyl oleate, lecithin and the like. Examples of base materials used for suppositories include, for example, cacao butter, emulsified cacao butter, lauric lipid, witepsol.

The dose and frequency of administration of the medicament of the present invention are not particularly limited, and they may be appropriately chosen depending on conditions such as a purpose of preventive and/or therapeutic treatment, a type of a disease, the body weight or age of a patient, severity of a disease and the like. Generally, a daily dose for oral administration to an adult may be 0.01 to 1,000 mg (the weight of an active ingredient), and the dose may be administered once a day or several times a day as divided portions, or once in several days. When the medicament is used as an injection, administrations may preferably be performed continuously or intermittently in a daily dose of 0.001 to 100 mg (the weight of an active ingredient) to an adult.

CHEMICAL EXAMPLES Example 1 Compound No. 4 of Table 1 6-Chloro-N-(2-phenylethyl)pyrazin-2-amine 4-oxide

A suspension of 0.330 g (2.0 mmol) of 2,6-dichloro-pyrazine 4-oxide in 0.485 g (4.0 mmol) of phenethylamine was allowed to stir under reflux for 10 min. pCooled water was added and the mixture extracted with dichloromethane, dried over sodium sulfate and evaporated to dryness. pThe residue obtained was purified by chromatography on silica gel eluting with a mixture of dichloromethane/methanol/diethylamine in the proportions 97/3/0.3 to give after trituration with diethyl ether 0.370 g (74%) of pure product as a grey solid.

Mp: 142-143° C.

RMN ¹H(CDCl₃; 200 MHz):

δ (ppm): 7.50 (s, 1H), 7.30-7.10 (m, 5H), 5.10 (br s, 1H), 3.60 (dd, 2H), 2.90 (dd, 2H).

Example 2 Compound No. 1 of Table 1 N-(2-phenylethyl)-6-pyridin-4-ylpyrazin-2-amine 4-oxide

A mixture containing 0.250 g (1.0 mmol) of 6-chloro-N-(2-phenylethyl)pyrazin-2-amine 4-oxide, 0.296 g (2.40 mmol) of 4-pyridine boronic acid, 0.60 mL (1.2 mmol) of a 2M solution of sodium carbonate in water and 0.116 g (0.1 mmol) of tetrakis(triphenylphosphine)palladium (0) in 5 mL of a mixture of ethanol/water in the proportions 5/1 was stirred under reflux for 16 h. Cooled water was added and the mixture extracted with dichloromethane, dried over sodium sulfate and evaporated to dryness. The residue obtained was purified by chromatography on silica gel eluting with a mixture of dichloromethane/methanol/diethylamine in the proportions 98/2/0.2 to give after trituration with diethyl ether 0.058 g (20%) of pure product as a yellow solid.

Mp: 184-185° C.

RMN ¹H(CDCl₃; 200 MHz):

δ (ppm): 8.70 (d, 2H); 7.90 (s, 1H); 7.70 (d, 2H); 7.45 (s, 1H); 7.30-7.00 (m, 5H); 4.80 (br t, 1H), 3.70 (m, 2H); 2.90 (t, 2H).

A list of chemical structures and physical data for compounds of the aforementioned formula (I), illustrating the present invention, is given in table 1. The compounds have been prepared according to the methods of the examples.

In the table, (Rot.) indicates the levorotatory or dextrorotatory properties of the enantiomeric compound.

TABLE 1 No. Rot

R1 R3 R2 Mp° C. salt 1

H H 184-185 Free base 2 (+/−)

H H 224-225 Free base 3 (+/−)

Cl H H 175-176 Free base 4

Cl H H 142-143 Free base

Test Example Inhibitory Activity of the Medicament of the Present Invention Against GSK3β

Four different protocols can be used.

In a first protocol: 7.5 μM of prephosphorylated GS1 peptide and 10 μM ATP (containing 300,000 cpm of ³³P-ATP) were incubated in 25 mM Tris-HCl, pH 7.5, 0.6 mM DTT, 6 mM MgCl₂, 0.6 mM EGTA, 0.05 mg/ml BSA buffer for 1 hour at room temperature in the presence of GSK3beta (total reaction volume: 100 microliters).

In a second protocol: 4.1 μM of prephosphorylated GS1 peptide and 42 μM ATP (containing 260,000 cpm ³³P-ATP) were incubated in 80 mM Mes-NaOH, pH 6.5, 1 mM Mg acetate, 0.5 mM EGTA, 5 mM 2-mercaptoethanol, 0.02% Tween 20, 10% glycerol buffer for 2 hours at room temperature in the presence of GSK3beta.

In a third protocol: 7.5 μM of prephosphorylated GS1 peptide and 10 μM ATP (containing 300,000 cpm of ³³P-ATP) were incubated in 50 mM Hepes, pH 7.2, 1 mM DTT, 1 mM MgCl₂, 1 mM EGTA, 0.01% Tween 20 buffer for one hour at room temperature in the presence of GSK3beta (total reaction volume: 100 microliters).

In a fourth protocol: 7.5 μM of prephosphorylated GS1 peptide and 10 μM ATP (containing 300,000 cpm of ³³P-ATP) were incubated in 50 mM Hepes, pH 7.2, 1 mM DTT, 1 mM MgCl₂, 1 mM EGTA, 0.01% Tween 20 buffer for 90 minutes at room temperature in the presence of commercial GSK3beta (Millipore) (total reaction volume: 100 microliters).

Inhibitors were solubilized in DMSO (final solvent concentration in the reaction medium, 1%).

The reaction was stopped with 100 microliters of a solution made of 25 g polyphosphoric acid (85% P₂O₅), 126 ml 85% H₃PO₄, H₂O to 500 ml and then diluted to 1:100 before use. An aliquot of the reaction mixture was then transferred to Whatman P81 cation exchange filters and rinsed with the solution described above. Incorporated ³³P radioactivity was determined by liquid scintillation spectrometry. The phosphorylated GS-1 peptide had the following sequence: NH2-YRRAAVPPSPSLSRHSSPHQS(P)EDEE-COOH. (Woodgett, J. R. (1989) Analytical Biochemistry 180, 237-241.

The GSK3β inhibitory activity of the compounds of the present invention are expressed in IC₅₀, and as an illustration the range of IC₅₀'s of the compounds in table 1 are between 0.1 nanomolar to 3 micromolar concentrations.

For example, on the protocol 3, the compound No. 2 of table 1 shows an IC₅₀ of 0.506 μM.

Formulation Example

(1) Tablets

The ingredients below were mixed by an ordinary method and compressed by using a conventional apparatus.

Compound of Example 1  30 mg Crystalline cellulose  60 mg Corn starch 100 mg Lactose 200 mg Magnesium stearate  4 mg (2) Soft Capsules

The ingredients below were mixed by an ordinary method and filled in soft capsules.

Compound of Example 1 30 mg Olive oil 300 mg  Lecithin 20 mg (3) Parenteral Preparations

The ingredients below were mixed by an ordinary method to prepare injections contained in a 1 ml ampoule.

Compound of Example 1 3 mg Sodium chloride 4 mg Distilled water for injection 1 ml

INDUSTRIAL APPLICABILITY

The compounds of the present invention have GSK3β inhibitory activity and are useful as an active ingredient of a medicament for preventive and/or therapeutic treatment of diseases caused by abnormal activity of GSK3β and more particularly of neurodegenerative diseases. 

1. A compound of formula (I):

wherein: R1 represents a 4-pyridine ring or a halogen atom; R2 represents a hydrogen atom; R3 represents a hydrogen atom; R4 represents: a phenylC₁₋₃alkyl group, this group being optionally substituted by 1 to 4 substituents selected from a C₁₋₆ alkyl group, a halogen atom, a C₁₋₂ perhalogenated alkyl group, a C₁₋₃ halogenated alkyl group, a hydroxyl group, a C₁₋₆ alkoxy group, a C₁₋₂ perhalogenated alkoxy group, a C₁₋₆ alkylsulfonyl group, a nitro, a cyano, an amino, a C₁₋₆ monoalkylamino group, a C₂₋₁₂ dialkylamino group, an acetoxy group, and an aminosulfonyl group; and R5 represents a hydrogen atom; or a pharmaceutically acceptable salt thereof.
 2. The compound of formula (I) according to claim 1:

wherein: R1 represents a 4-pyridine ring or a halogen atom; R2 represents a hydrogen atom; R3 represents a hydrogen atom; R4 represents: a phenylC₁₋₃alkyl group, this group being optionally substituted by 1 to 4 substituents selected from a halogen atom and a hydroxyl group; and R5 represents a hydrogen atom; or a pharmaceutically acceptable salt thereof.
 3. The compound according to claim 1 selected from the group consisting of: N-(2-phenylethyl)-6-pyridin-4-ylpyrazin-2-amine 4-oxide; (+/−)2-[(4-oxido-6-pyridin-4-ylpyrazin-2-yl)amino]-1-phenylethanol; (+/−)6-2-[(6-chloro-4-oxidopyrazin-2-yl)amino]-1-phenylethanol; and 6-chloro-N-(2-phenylethyl)pyrazin-2-amine 4-oxide.
 4. A pharmaceutical composition comprising a compound of formula (I) according to claim 1 or a pharmaceutically acceptable salt thereof and one or more pharmaceutical additives.
 5. A pharmaceutical composition comprising a compound of formula (I) according to claim 2 or a pharmaceutically acceptable salt thereof and one or more pharmaceutical additives.
 6. A pharmaceutical composition comprising a compound according to claim 3 or a pharmaceutically acceptable salt thereof and one or more pharmaceutical additives. 